The preparation of dynamically partially crosslinked thermoplastic elastomers from (i) a propylene polymer material, (ii) an amorphous ethylene/propylene copolymer rubber, and (iii) a semicrystalline, essentially linear ethylene copolymer is described in U.S. Pat. Nos. 4,948,840; 5,143,978, and 5,196,462. A fourth component, polybutene-1, is included in the composition of U.S. Pat. No. 5,143,978 and is optional in U.S. Pat. No. 5,196,462.
Olefinic thermoplastic elastomers have been used in various extrusion applications such as films, sheet, wire coating, profile extrusions, and other shaped articles. In many cases material builds up on the die face during extrusion. This is undesirable, since the material that has built up can come loose and stick to the article being extruded or formed. The unwanted material is not easily removed and causes disruptions in the usually continuous process. If it is not removed, it causes disruption in the collection of the article being extruded, since the article is usually collected on a roll. In some cases, if the stuck piece is not removed, it can lead to premature failure of the article during service. Thus, there is a need to minimize or prevent buildup of any material on the die face during extrusion of thermoplastic elastomers without significantly affecting the properties or performance of the material or extruded article.